Tropical Atlantic Variability (TAV)

Fluctuations in the strength of the trade and cross equatorial winds in the Tropical Atlantic, associated with changes in interhemispheric SST gradient (Fig. 1). These have a large impact on precipitation over Northeast Brazil, Sahel, and the Guinea coastal region.

Figure 1: see legend above.

Understanding the cause of the fluctuations shown in Fig. 1 is made difficult by the various processes potentially impacting Tropical Atlantic variability (i) the influence of the NAO (ii) the remote forcing from ENSO (iii) local air - sea interactions over the tropical Atlantic sector.

In addition to off-equatorial SST anomalies, tropical Atlantic variability has also a component along the equator, which may be related to modulation in the strength of the oceanic subtropical cell (Inui and Malanotte-Rizzoli, 2000, Fig. 2).

Figure 2: (top) model simulations of SST anomalies along the equator, showing alternating warm and cold episodes, each persisting for several years. (below) the mean subtropical cell simulated by the model (latitude - depth plot of the circulation, every Sverdrup). The fluctuations in this cell might contribute to the SST variability seen on the left. From Inui and Malanotte - Rizzoli (2000).